The "Marinizing" Process - Continued

Marine motor manufacturers (those who are in the
business of selling ready-to-go "marinized" engines) often make
additional modifications that aren't as easy for the individual converting
his own engine. For example, cams may be changed or re-ground in order to
change torque and horsepower characteristics so they will be more suitable for
boat use. Carburetors may also be changed or modified, since on a boat the
carburetor may operate at half or full throttle most of the time, which may be
unlike an automotive carburetor that must operate over a variety of
settings.

Fig. 3-13: A typical
"bobtail" marine engine conversion kit. With this type of
installation, a marine transmission is not used. (Courtesy of Glenwood Marine
Equipment)

For those who want to convert their own gasoline
engine to marine use, the following will outline the process. Note that this
process is basically the same one that a marine motor manufacturer will use in
"marinizing" a motor that will end up as a so-called
"marine" motor. Basically, the conversion process involves adding,
deleting and changing parts, many of which are external or "bolt-on"
in nature. A typical marine conversion "kit" may consist of:

Water cooled exhaust manifolds

Marine water pump

Carburetor tilt shim or angle plate (perhaps)

Carburetor flame arrestor or "backfire" trap

Brass freeze plugs (for saltwater use)

Engine mounts

Fig. 3-14: A completed
"bobtail" conversion of an automotive V-8. This engine will be used
in a stern-mounted v-drive installation without a marine transmission. Note the
hoses connecting to the exhaust elbows from the top of the engine block, and
the water pump driving off the end of the camshaft. (courtesy of Nicson
Engineering)

In addition to these components, depending on the
engine, other parts might include an oil filter relocation kit, oil coolers,
water cooled exhaust risers or elbows, various cover plates, various hose and
plumbing assemblies, various brackets and pulleys, starter shaft extensions,
lifting rings, and other items. In some cases, the oil pan will be replaced
because of shape or material. Ordinarily, automotive pans are stamped sheet
metal, which can corrode quickly if in contact with seawater in the bilge.
Heavier cast iron pans are better in this respect. Also, a pan of greater
capacity may be required for marine use, or a reshaped pan may be necessary due
to the boat's structure interfering, or because the shaft angle is so
severe that the oil sump will be poorly located to provide positive
lubrication.

Fig. 3-15 & 3-16: Typical water cooled
exhaust manifolds as used in a marine engine conversion. These manifolds are
made from light weight cast aluminum, shown in traditional "log" and
"header" styles.

1 - Water-Cooled Exhaust Manifolds

In the typical engine used for shore-side purposes,
the exhaust manifolds are cooled by air alone. However, in a boat where the
engine is often confined within closed spaces, this heat is hazardous. Also,
the heat may cause the engine to overheat and hamper engine breathing.
Consequently, the exhaust manifolds must be cooled, and this is done with water
jacketed manifolds. These are perhaps the most obvious aspect of the marinized
engine. In some limited uses, especially for competition boats where weight is
important, and the engine is not completely confined, air cooled manifolds (or
"dry stacks" as they are called) may be used (see Chapter 15). In
normal boats, however, this practice is not safe.

2 - Marine Water Pump

The automotive-type engine uses a water pump that
is the recirculating type. It is not intended to pump water, but to circulate
it instead. On the other hand, the marine water pump must be capable of pumping
water into the engine's cooling system. Furthermore, it must be able to
stand up to marine conditions, such as salt water, without corroding. Most
marine water pumps are of the "Neoprene" hard rubber impeller type
that can stand up to sand and silt. The water pump may be fitted on special
brackets or fitted in the allotted space for the automotive type it replaces.
The pump may be driven with pulleys and vee belt, or directly off the engine
cam. Usually the marine pump runs at a considerably slower speed than the
motor.

3 - Carburetor Tilt Shim

In many marine motor installations, the engine is
often set at some angle from the horizontal. This is quite unlike, for example,
an automotive installation where the engine is basically level most of the
time. Since gasoline engine carburetors are intended for level operation, the
tilt shim is used to bring the carburetor back to its correct plane of
operation. Tilt shims are available for many different angles depending on the
installation angle. They are also available for a wide range of carburetors and
number of barrels or throats. If the engine is mounted horizontally, a tilt
shim is not necessary.

Fig. 3-17: A carburetor backfire flame arrestor
is a necessary part of gasoline engine conversions for safety. Such units
prevent flames from the engine during backfiring which could ignite volatile
gasoline fumes that might accidently enter the engine compartment.

4 - Carburetor Flame Arrestor

An air cleaner is not required on a marine motor
because it operates in basically clean air surroundings. Since a gasoline
powered engine can backfire on occasion, this presents a potential hazard of
fire or explosion aboard a boat, especially if there is no air cleaner.
Consequently, the air cleaner is replaced with an approved-type flame arrestor
that prevents this condition from being dangerous. These units are available in
a wide range of types and sizes to adapt to various carburetors. Always allow
ample clearance above downdraft carburetor flame arrestors for sufficient air
to reach the engine.

5 - Brass Freeze Plugs

Automotive and other similar type engines have
machined holes in the block or cylinder head for use in fabricating the engine.
These holes are plugged with freeze or expansion plugs usually made from steel.
When engines are used in salt water, these steel plugs will rust and fail
rapidly, and consequently should be replaced with solid brass plugs (but not
brass plated steel plugs!). Only those plugs which will be in contact with
corrosive conditions need be replaced, however.

6 - Engine Mounts

Because the engine will usually fit to motor
stringers or similar mounting members, special mounts are required for most
conversions. Such mounts may be separate components, or built in as part of
other components, such as the flywheel cover. Either rigid or rubber type
flexible mounts may be used, with the four-point mounting being common.

7 - Oil Filter Relocation Kit

With many converted engines, the standard location
for the oil filter could make it inaccessible. Therefore, kits are available to
relocate the filter to a more convenient location. In addition to the filter, a
water cooled oil cooler is frequently added in line with the filter unit. Oil
temperatures often exceed those found in automobiles due to the lack of air
flow.

8 - Water-Cooled Exhaust Risers & Elbows

Water-cooled exhaust elbows or risers are usually
required in conversions. The elbows direct the exhaust downward so that the
cooling water can be exhausted through the exhaust line without backing up into
the engine, which would damage the engine. Similarly, the elbows also provide
backflow protection in the event that water enters the exhaust line from the
back of the boat. If the engine is located deep in the hull or so the exhaust
manifold water outlet would be too low to have a proper downward slope, risers
would be used instead of elbows.

9 - Cover Plates

Depending on the engine and the conversion kit,
various cover plates may be required. Water cooled manifolds often have cover
plates on the ends with threaded adapters where the cooling water hoses are
connected. Flywheel covers are often fitted which may also serve as engine
mounts, as well as being machined for mounting the starter motor. Timing gear
covers are sometimes available with provisions for mounting a cam driven water
pump. For safety, cover plates are often available for covering pulleys and vee
belts.

10 - Starter Extensions

On some conversions, the starting motor, if left in
its original position, could be subjected to moisture and splashing bilge
water, or may be in a position that is difficult to service due to the
angularity of the motor when installed. In these cases, starter extensions are
sometimes available which relocate the starter to a more forward or higher
location on the engine.

WHAT ABOUT THE TRANSMISSION?

A consideration with most marine engines is the
need for some type of transmission. These are discussed in detail in Chapter 4,
however, in many conversion kits, they may be part and parcel to the conversion
process, and therefore may require advance thought on the part of the purchaser
of an engine or conversion kit. As will be pointed out later, the standard
automotive transmission is not really practical for marine use and is therefore
dispensed with, together with the clutch. Automatic transmissions found on
automobiles also fall into this category, although there are some exceptions.
Since a boat does not have brakes, usually some sort of transmission
arrangement must be provided so that reverse can be engaged to slow or stop the
boat. Consequently a marine transmission is frequently coupled to the end of
the engine.

If a transmission is not coupled to the engine, the
engine is called a "bobtail" engine. The "bobtail" engine
is used with sterndrive units, jet drives, and in certain v-drive installations
where the transmission function is a part of the v-drive. In certain
competition boats, a "bobtail" engine without a transmission of any
type is used. In other words, the engine is started in gear and the boat takes
off as soon as the engine is started. The only way to stop such boats is to
shut off the engine. Obviously, such a boat is dangerous and the practice is
restricted to racing boats operating under controlled conditions. Basically,
the "bobtail" engine consists of a flywheel housing for enclosing the
flywheel, and usually to provide the rear mounts of the engine. A drive shaft
or coupling is also necessary to connect the flywheel to the power transmission
system, be it a jetdrive, sterndrive, or v-drive.